This is very similar to a light Hollandaise sauce. It is excellent on a variety of cooked vegetables and especially fine for making deviled eggs.

1 egg yolk
3/4 c. plain low fat yogurt
2 tbsp. fresh lemon juice
1/4 tsp. salt
1/8 tsp. dry mustard

Beat egg yolk slightly in a heavy saucepan with 1/4 cup yogurt, lemon juice, salt, and mustard. Cook over low heat, stirring constantly until thick and smooth. Remove from heat. Slowly stir in remaining 1/2 cup yogurt; blend well. Serve warm over vegetables or store in a covered jar in refrigerator. Reheat gently over low flame. 1 serving: 1 1/2 tablespoons.